Insufficient consumption of micronutrients and common mental disorders in Brazilian adolescents

The study aimed to estimate the association of insufficient consumption of vitamins A, C, E, B12 and zinc on the pathogenesis of Common Mental Disorders (CMD) in Brazilian adolescents who participated in the Estudo de Riscos Cardiovasculares em Adolescentes ERICA (Study of Cardiovascular Risks in Adolescents) from February 2013 to November 2014. The sample corresponded to the number of students (71,971) who answered the the 24-hour dietary recall and the questionnaire that addressed mental health. Pearson’s chi-square test and multivariate logistic regression analysis were performed between the CMD variable and insufficient micronutrient consumption, adjusting for sex, type of school and age group variables. The level of significance adopted was p<0.05. Associations between the existence of CMD and insufficient consumption of Vitamin B12 and zinc were significant. Zinc, when consumed in small quantities, was the element that most influenced the CMD variable. Therefore, it was found that insufficient consumption of Vitamin B12 and zinc influences the presence of CMD in adolescents.


MATERIALS AND METHODS
Study characterization We conducted a cross-sectional study with data from the Estudo de Riscos Cardiovasculares em Adolescentes -ERICA (Study of Cardiovascular Risks in Adolescents), a multicenter, nationwide survey carried out with adolescents aged 12 to 17, from elementary or high school, from public and private schools, between February 2013 and November 2014.

Population of interest and sample
The ERICA population was stratified into 32 geographic strata, with 27 capitals and five groups with the other municipalities in each macro-region. Schools from 124 municipalities were selected, corresponding to a total of 3,753 classes, in 1,247 schools 9 .
Of the 102,327 eligible adolescents registered in the selected schools, 71,971 (70.3%) participated in this investigation, who answered the 24 hour dietary recall (R24h) and the questionnaire regarding mental health. Adolescents who did not belong to the age group of interest, pregnant adolescents and those who were unable to answer the questionnaires because they were mentally disabled were excluded from the analysis 9 .
Data collection Data were collected using a self-administered questionnaire 10 . For the present study, the following variables were explored: sex, age, type of school, CMD and intake of the following micronutrients: vitamins A, C, E, B 12 and zinc. The age variable was used categorically, considering two groups: 12-14 years and 15-17 years.
To assess CMD, the General Health Questionnaire, 12 item version, was used 10 . The scores of the individual items present in the questionnaire were coded as "absent" or "present" (0 or 1, respectively) and then added together; adolescents with a score of three or more were classified as cases of CMD 11 . Food intake was estimated by applying a R24h. Specific software was used to enter food consumption data 12 and the interview technique applied was the multiplepass method 13 , which aims to reduce the underreport of food consumption. Nutrient intake data did not include consumption of supplements or medications 12 .

Statistical analysis
The prevalence of inadequate consumption of micronutrients (vitamins A, C, E, B 12 and zinc) was based on R24h data and estimated as the proportion of adolescents with intake below the estimated average need, using the Estimated Average Requirement -EAR method, as recommended by the Institute of Medicine 14 . For the calculation of inadequacy, the sample weight and the complexity of the sample design were considered, using the Balanced Repeated Replication technique with Fay modification 15 . The intra-individual variability was corrected according to the method proposed by the National Cancer Institute (NCI) 16 .
Data analysis was performed using the Stata ® software (Statacorp, College Station, Texas, USA), version 12.0, using the survey module, considering complex sample data analysis. The Pearson chi-square test was used to assess the existence of an association between the variables of insufficient consumption of vitamins A, C, E, B 12 and zinc with sex, type of school and age group. The Odds Ratio (OR) was calculated, with a 95% confidence interval (CI), estimated by the logistic regression model, to measure the strength of association between the variables. Crude OR 's were estimated and adjusted for sex, type of school and age group. Multivariate logistic regression analysis was performed between the dependent variable (CMD) and insufficient micronutrient consumption (crude model) and then adjusted for sex, type of school and age group variables (adjusted model). The variables that showed statistical significance in the crude and adjusted models made up the final model. The level of significance adopted was 5%.

Ethical aspects
The ERICA was approved by the Research Ethics Committee of the Institute of Studies in Collective Health, from the Federal University of Rio de Janeiro (Opinion nº 01/2009; Process 45/2008) and by the Research Ethics Committees of each 27 participating institutions, one in each unit of the Brazilian federation. The adolescents who agreed to participate and whose parents signed the informed consent form participated in the study.

RESULTS
The results show: CMD associations with sex, type of school and age group; associations of insufficient consumption of micronutrients in relation to sex, type of school, age group and CMD; and a multiple logistic regression model, which estimates which micronutrients contribute to the presence of CMD, when consumed insufficiently.
Mental disorders were more prevalent in female adolescents, from public schools and aged 15 to 17 years. Significant associations were found between CMD, sex and age group (Table 1).
High prevalence of insufficient nutrient consumption was observed, which was significantly associated with sex, with the exception of Vitamin C. The highest percentages of inadequate consumption of Vitamins E, B 12 and zinc occurred among females ( Table 2).
Public school students had higher percentages of insufficient consumption of Vitamins A, C and B 12 compared with private school students. Associations of these nutrients with the type of school variable were significant (p<0.001). However, although the association has not been shown significant for vitamin E and zinc, attention is paid to the high percentages of insufficient consumption of these elements in public and private schools, table 2.
Older adolescents had higher percentages of insufficient consumption of micronutrients, except zinc. Significant differences were observed in relation to the low consumption of Vitamin E and B 12 and age group ( Table 2).
Significant associations between CMD and insufficient consumption of Vitamin A, B 12 and zinc were observed (Table 3). In an adjusted model, vitamin B 12 and zinc lost their significance in the association, while vitamin A maintained the previously observed relationship ( Table 3).
Analyzing the statistical data of multiple logistic regression (Table 4), it was possible to observe that the insufficient consumption of vitamin A and zinc were the ones that most influenced the CMD variable. In a crude model, consumers with an insufficient amount of food sources of zinc had higher chances of CMD (OR: 1.18; 95% CI: 1.06 -1.33; p -value: 0.004), while consumers with an insufficient amount of vitamin A were less likely (OR: 0.76; 95% CI: 0.68-0.86).
When the model was adjusted by sex, type of school and age group, insufficient consumption of vitamin A maintained the relation of the crude model while zinc lost its significance. In addition, it was observed that women and those aged between 15 and 17 years were more likely to have CMD.
In the analysis of the final model, it was observed that insufficient consumption of zinc returned to have significance in the association with CMD, being the element that, when consumed in small quantities, most influenced the existence of CMD.

DISCUSSION
Associations found between micronutrient intake and CMD have been, in general, derived from investigations carried out in adults or the elderly. This is the first study developed, based on ERICA, which analyzed data on mental morbidity in adolescents and its relationship with insufficient consumption of micronutrients.
Inadequate eating habits may reflect insufficient consumption of micronutrients, which, in turn, can trigger several metabolic changes that can result in various pathologies, including psychiatrics 4 .
Population-based review studies conducted in different parts of the world show that approximately one-third of adolescents experience some CMD throughout their lives. These studies point to higher prevalence of CMD among girls, while boys have higher rates of behavioral and conduct mental disorders varying with the degree of income and development of countries 17,18,19 .
Anxiety and depression are the most common psychiatric disorders induced by increased oxidative stress and damage to brain cells. Non-enzymatic antioxidants, such as vitamins E (alphatocopherol), C (ascorbic acid), β-carotene, zinc, among others, minimize the production of free radicals that damage cells and, thus, to combat excessive oxidation, in addition to the antioxidant defense in the biological system 20,21 . Studies associate CMD with reduced concentrations of antioxidant compounds and suggest that supplementation of these elements may be useful as adjunctive therapy in patients with stress-induced mental disorders, as they suppress neuroinflammation and oxidative stress 20,22,23 .
The result obtained in the present investigation, regarding the association of vitamin A and CMD, was different to what has been reported in the literature 20,21,22,23 . Methodological differences may justify this finding, such as: instruments and methods used to determine food consumption and mental disorders, age group of the participants, sample and statistical analysis. On the other hand, our results that report the positive association between insufficient consumption of Vitamin B 12 , zinc and CMD in adolescents, are concordant with research carried out in children, adults and the elderly in different countries 24,25,26 .
Vitamin B 12 is a methyl donor in many methylation reactions in the brain. According to the hypomethylation hypothesis, it is essential for the transmethylation of neuroactive substances such as myelin and monoamine neurotransmitters. Thus, the lack of synthesis and/or changes in the cobalamin-dependent metabolic cycle has been implicated as pathogenic mechanisms in central nervous system disorders, associated with depression, bipolar disorder, panic disorder psychosis and phobias 27,28,29,30 . Recent studies emphasize the possible role of zinc in neurotransmitter systems, particularly serotonergic and glutamatergic systems, as well as in antioxidant mechanisms, neurotrophic factors and neuronal precursor cells. Thus, zinc deprivation influences cerebral zinc homeostasis leading to psychiatric symptoms, including, in addition to depression, impaired cognition and learning difficulties 31,32,33,34 .
Some investigations corroborate the inverse relationships between dietary zinc intake and depression in female individuals found in the present study 35,36 .
A new study, conducted at the University of California, points out that females are almost twice as chances to develop depression. The researchers found that women who had received small doses of endotoxins (substances that promote controlled brain inflammation) had a reduction in the activity of a set of structures that promote the sensation of pleasure and that, in depression, is inhibited. The same did not happen with the men who took the endotoxins and with the entire placebo group 36 .
Finally, although this study used validated instruments for diagnosing CMD and food intake, limitations should be considered, namely: other variables that may influence the mental health of individuals such as body mass index, activity physical practice, alcohol and drug use, medications and hours of sleep were not included in our models. The adjustments used in the statistical analyses were different from other studies-some adjusted for BMI, physical activity, energy, while others did not; and the methods of assessing CMD were different from other original studies, which were based on rating scales.
In conclusion, the present investigation showed that insufficient consumption of Vitamin B 12 and zinc are associated with the presence of CMD in adolescents. Furthermore, carrying out prospective and controlled studies would be important to obtain a more precise interpretation of the relationship between micronutrient consumption and CMD in this population subgroup. Acknowledgements: Thank you to the ERICA (Study of Cardiovascular Risk Factors in Adolescents) Publications Committee for authorizing the completion of the study and providing the data for its execution according to project number 1509380527.

Conflicts of interests:
The authors declare that they have no conflict of interest.